<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let money = 100
        let op = 0
        while(op !== 4){
        op = +prompt(`
            请您选择操作：
            1.存钱
            2.取钱
            3.查看余额
            4.退出
        `)
        switch(op){
            case 1:
                money += +prompt(`输入您想存入的金额：`)
                break
            case 2:
                money -= +prompt(`输入您想取出的金额：`)
                break
            case 3:
                alert(`您的余额为${money}元`)
                break
            case 4:
                break
        }
        }
    </script>
</body>
</html>